Liquid crystal display device and manufacturing method of liquid crystal display device

ABSTRACT

To sophisticate a portable electronic appliance without hindering reduction of the weight and the size, more specifically, to sophisticate a liquid crystal display apparatus installed in a portable electronic appliance without hindering the mechanical strength, a liquid crystal display apparatus includes a first plastic substrate, a light-emitting device which is disposed over the first plastic substrate, resin which covers the light-emitting device, an insulating film which is in contact with the resin, a semiconductor device which is in contact with the insulating film, a liquid crystal cell which is electrically connected to the semiconductor device, and a second plastic substrate, wherein the semiconductor device and the liquid crystal cell are disposed between the first plastic substrate and the second plastic substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display apparatus, andmore particularly such a transparent liquid crystal display apparatusinstalled in a portable electronic appliance. Further, the inventionrelates to a method for manufacturing a liquid crystal displayapparatus, and more particularly such a method for manufacturing atransparent liquid crystal display apparatus installed in a portableelectronic appliance. Moreover, the invention relates to an electronicappliance using the liquid crystal display apparatus.

2. Related Art

A portable electronic appliance as typified by a portable phone or anelectronic book is required to have various functions such as sendingand receiving mail, recognizing sound, and capturing an image using asmall camera, in addition to a flat panel display for displaying animage. On the other hand, there is still a strong demand by user such asreducing size and weight. Therefore there is a need for installing IChaving further large size of circuit or amount of memory as much aspossible into limited volume of a portable electronic appliance.

It is important how to manufacture a flat panel display into thin andlight in order to keep space to accommodate IC and to reduce size andweight of a portable electronic appliance. For instance, a liquidcrystal display apparatus used relatively a lot for a portableelectronic appliance can be in some degree reduced its size and weightby reducing a thickness of a glass substrate used for a panel filledwith liquid crystal and by adopting a reflective type liquid crystaldisplay apparatus that needs no light source, an optical waveguide, orthe like.

However, a glass substrate cannot be formed into too thin consideringmechanical strength of a panel. For instance, in case of using bariumborosilicate glass, alumino borosilicate glass, or the like, thicknesslimit and weight limit of 3-inch-square is at most from 1 to 2 mm and 10g, respectively. A reflective type liquid crystal display apparatusutilizing outside light is difficult in recognition of an image in thedark so that an advantage that a portable electronic appliance is notrequired to be site-specific is not sufficiently utilized.

SUMMARY OF THE INVENTION

It is an object of the present invention is to sophisticate a portableelectronic appliance without hindering reduction of the weight and thesize. It is more specific object of the invention is to sophisticate aliquid crystal display apparatus installed in a portable electronicappliance without hindering the mechanical strength.

A liquid crystal display apparatus according to the invention uses alight-emitting device such as a light-emitting diode (LED) or anelectroluminescent device as a light source. The light-emitting deviceformed over a plastic substrate having flexibility is covered with aresin that is transparent to light in order to flatten a surface of thelight-emitting device. Then, a liquid crystal cell and a semiconductordevice for driving the liquid crystal cell are provided over theflattened resin. A light source in a state that a light-emitting deviceis covered with a resin is referred to as a solid-state light source.

Generally, a plastic substrate is superior in mechanical strength forvibration and shock by its flexibility so that the thickness can easilybe reduced. However, a plastic substrate and a resin often have notenough heat resistance to withstand heat treatment in manufacturing asemiconductor device used for a liquid crystal display apparatus. Inview of this, according to the invention, a semiconductor device isformed over a substrate having resistance enough to withstand the heattreatment, and the semiconductor device is moved over a solid-statelight source.

A liquid crystal display apparatus according to the invention isprovided with a means of reflecting light generated in a light-emittingdevice in a direction of a liquid crystal cell. Specifically, light isreflected by pasting a ready-made reflection plate over the plasticsubstrate or by depositing a metal film (hereinafter, reflection film)over a surface of the plastic substrate by vapor deposition. Further, apolarization plate is provided between a resin covering a light-emittingdevice, and a semiconductor device and liquid crystal cell.

Hereinafter, the first method for manufacturing a liquid crystal displayapparatus according to the invention will be explained in specific.

A first substrate that has heat resistance capable of withstanding heattreatment in a process for manufacturing a semiconductor device isprepared. A metal film is formed over the first substrate, and oxidizedto form a metal oxide film having an extreme thin film thickness ofseveral nm. Then, an insulating film and a semiconductor film aresequentially stacked over the metal oxide film. The insulating film canbe formed into either a single layer or a laminated layer composed of aplurality of films. For instance, silicon nitride, silicon oxynitride,silicon oxide, or the like can be used for the insulating film. Asemiconductor device used for a liquid crystal display apparatus isformed by the semiconductor film.

After the semiconductor device is formed and before completing a liquidcrystal cell, a second substrate is pasted onto the first substrate tocover the semiconductor device in such a way that the semiconductordevice is sandwiched between the second substrate and the firstsubstrate. The liquid crystal cell includes a pixel electrode, a counterelectrode, and liquid crystal disposed between the pixel electrode andthe counter electrode. As used herein, the term “before completing aliquid crystal cell” refers to a period between the formation of a pixelelectrode of a liquid crystal cell connected electrically to a TFT,which is one of semiconductor devices, and an orientation film coveringthe pixel electrode, and the paste of a counter substrate provided witha counter electrode.

A third substrate is pasted for reinforcing rigidity of the firstsubstrate onto an opposite side of the first substrate on which thesemiconductor device is formed. The first substrate can be easilyseparated and the semiconductor device is hardly damaged when rigidityof the first substrate is stronger than that of the second substrate. Inaddition, the third substrate is unnecessary to be pasted in case thatrigidity of the first substrate is enough to separate the firstsubstrate from the semiconductor device.

Then, the metal oxide film is crystallized by heat treatment or the liketo enhance brittleness of the metal oxide film and to make it easier forthe first substrate to be easily separated from the semiconductordevice. Subsequently, the first substrate is separated together with thethird substrate from the semiconductor device. In addition, the heattreatment to crystallize the first substrate can be carried out beforepasting either the third substrate or the second substrate.Alternatively, the heat treatment in a process for forming thesemiconductor device can serve as the heat treatment to crystallize themetal oxide film.

The first substrate may be separated together with the third substratefrom the semiconductor device by splitting-off a boundary face of themetal film and the metal oxide film, the boundary face of the insulatingfilm and the metal oxide film, or metal oxide film itself. In any case,the first substrate is separated so as the semiconductor device toattach to the second substrate.

A plastic substrate at the side of a light source is prepared for beingpasted with a semiconductor device. Hereinafter, the plastic substrateis referred to as a device substrate to distinguish from a plasticsubstrate at the side of a counter electrode used in later. Alight-emitting device is provided over the device substrate, and a resinis coated to cover the light-emitting device. Then, a first polarizationplate is pasted onto the resin that is flattened.

Next, by separating the first substrate, the semiconductor deviceattached to the second substrate is pasted onto the first polarizationplate with adhesive or the like. Then, the second substrate is separatedto fix the semiconductor device to the device substrate.

A liquid crystal cell for a liquid crystal apparatus is formed.Specifically, a plastic substrate provided with a counter electrode, asecond polarization substrate, or the like (hereinafter, countersubstrate) is prepared separately, and pasted onto the semiconductordevice, then, a liquid crystal cell is completed. A color filter, anorientation film, a black matrix, and the like may be provided to thecounter substrate in addition to the counter electrode and the secondpolarization plate.

Hereinafter, a second method for manufacturing a liquid crystal displayapparatus according to the invention will be explained.

A first substrate that has heat resistance capable of withstanding heattreatment in a process for manufacturing a semiconductor device isprepared. A metal film is formed over the first substrate, and oxidizedto form a metal oxide film having an extreme thin film thickness ofseveral nm. Then, an insulating film and a semiconductor film aresequentially stacked over the metal oxide film. The insulating film canbe either a single layer or a laminated layer having a plurality offilms. For instance, silicon nitride, silicon oxynitride, silicon oxide,or the like can be used for the insulating film. A semiconductor deviceused for a liquid crystal display apparatus is formed by thesemiconductor film.

A liquid crystal cell for a liquid crystal apparatus is formed. Theliquid crystal cell includes a pixel electrode, a counter electrode, andliquid crystal disposed between the pixel electrode and the counterelectrode. Specifically, a plastic substrate provided with a counterelectrode, a second polarization substrate, or the like (hereinafter,counter substrate) is prepared separately, and pasted onto thesemiconductor device, then, a liquid crystal cell is completed. A colorfilter, an orientation film, a black matrix, and the like may beprovided to the counter substrate in addition to the counter electrodeand the second polarization plate.

After forming the semiconductor device and the liquid crystal cell, asecond substrate is pasted onto the semiconductor device and the liquidcrystal cell so as to cover them. Accordingly, the liquid crystal cellis interposed between the first substrate and the second substrate.

A third substrate is pasted for reinforcing rigidity of the firstsubstrate onto an opposite side of the first substrate on which thesemiconductor device and the liquid crystal cell are formed. The firstsubstrate can be easily separated and the semiconductor device and theliquid crystal cell are hardly damaged when rigidity of the firstsubstrate is stronger than that of the second substrate. In addition,the third substrate is unnecessary to be pasted in case that rigidity ofthe first substrate is enough to be separated from the semiconductordevice.

Then, the metal oxide film is crystallized by heat treatment or the liketo enhance brittleness of the metal oxide film and to make it easier forthe first substrate to be easily separated form the semiconductordevice. Subsequently, the first substrate is separated together with thethird substrate from the semiconductor device. In addition, the heattreatment to crystallize the first substrate can be carried out beforepasting either the third substrate or the second substrate.Alternatively, the heat treatment in a process for forming asemiconductor device can serve as the heat treatment to crystallize themetal oxide film.

The first substrate may be separated together with the third substratefrom the semiconductor device and the liquid crystal cell bysplitting-off a boundary face of the metal film and the metal oxidefilm, the boundary face of the insulating film and the metal oxide film,or metal oxide film itself. In any case, the first substrate isseparated so as the semiconductor device and the liquid crystal cell toattach to the second substrate.

A plastic substrate at the side of a light source (device substrate) isprepared for being pasted with the semiconductor device and the liquidcrystal cell. A light-emitting device is provided over the devicesubstrate, and a resin is coated to cover the light-emitting device.Then, a first polarization plate is pasted onto the resin that isflattened.

Next, by separating the first substrate, the semiconductor device andthe liquid crystal cell attached to the second substrate is pasted ontothe first polarization plate with adhesive or the like. Then, the secondsubstrate is separated to fix the semiconductor device to the devicesubstrate. And then, a liquid crystal display apparatus is completed.

In case that a plurality of liquid crystal display apparatus is formedfrom one large substrate, the large substrate is diced to divide intothe plurality of liquid crystal display apparatus.

According to the invention, a thickness of a liquid crystal displayapparatus can be at least 0.6 mm and at most 1.5 mm.

As described above, the liquid crystal display apparatus is superior inmechanical strength for shock since the device substrate and the countersubstrate have flexibility compared with a glass substrate.Consequently, a thickness of the liquid crystal display apparatus caneasily be reduced. Further, the freedom of shape of the liquid crystaldisplay apparatus is increased since the device substrate and thecounter substrate have flexibility. Therefore a liquid crystal displayapparatus can be formed into a curved shape to be capable of pastingonto a kind of a columned bottle.

Light generated in the light-emitting device is dispersed by coveringthe light-emitting device with a resin that is transparent to light toequalize brightness of a pixel portion of a liquid crystal displayapparatus. Brightness can be further equalized by providing dispersionplate between a liquid crystal cell and a resin covering alight-emitting device.

According to the invention, a liquid crystal display apparatus can bedrastically formed into thin and reduced its weight without beingdamaged the mechanical strength by above described structure. Applying aliquid crystal display apparatus according to the invention to anelectronic appliance, a space for using IC can be kept large and anelectronic appliance can be sophisticated without preventing theelectronic appliance from being lightweight and downsized. Especially, aliquid crystal display apparatus according to the present invention isuseful for a portable electronic appliance since usability thereofbecomes improved by reducing the weight and the size. According to theinvention, even when size of a pixel portion of a liquid crystal displayapparatus is increased, weight thereof is almost same as that of aliquid crystal display apparatus using a conventional glass substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D are views showing cross-sectional views of a liquidcrystal display apparatus according to the invention;

FIGS. 2A to 2D are views showing cross-sectional views of a liquidcrystal display apparatus according to the invention;

FIGS. 3A to 3E are explanatory views showing a method of manufacturing aliquid crystal display apparatus according to the invention;

FIGS. 4A to 4C are explanatory views showing a method for manufacturinga liquid crystal display apparatus according to the invention;

FIGS. 5A and 5B are explanatory views showing a method for manufacturinga liquid crystal display apparatus according to the invention;

FIG. 6 is an explanatory view showing a method for manufacturing aliquid crystal display apparatus according to the invention;

FIGS. 7A to 7C are explanatory views showing a method for manufacturinga liquid crystal display apparatus according to the invention;

FIGS. 8A and 8B are explanatory views showing a method for manufacturinga liquid crystal display apparatus according to the invention;

FIGS. 9A and 9B are explanatory views showing a method for manufacturinga liquid crystal display apparatus according to the invention;

FIG. 10 is an explanatory view showing a method for manufacturing aliquid crystal display apparatus according to the invention;

FIGS. 11A and 11B are explanatory views showing a method formanufacturing a liquid crystal display apparatus according to theinvention;

FIGS. 12A to 12C are cross-sectional views showing a thin film circuitor an LED driver thin film circuit;

FIGS. 13A to 13D are cross-sectional views showing an electronic cardutilizing a liquid crystal display apparatus according to the invention;

FIGS. 14A and 14B are oblique perspective views showing a large devicesubstrate;

FIGS. 15A to 15D are views showing an LED utilizing an FPC and the statethat the LED is pasted onto a device substrate;

FIGS. 16A and 16B are views showing the structure of a device substrate;

FIGS. 17A and 17B are an oblique perspective view and a cross-sectionalview showing a sensor electronic card, respectively;

FIGS. 18A to 18F are views showing electronic appliances;

FIGS. 19A and 19B are cross sections of TEM images of a metal oxide filmbefore separating;

FIGS. 20A and 20B are cross sections of TEM images of an insulating filmafter separating; and

FIGS. 21A and 21B are cross-sectional views showing a liquid crystaldisplay apparatus according to the present invention.

These and other objects, features and advantages of the presentinvention will become more apparent upon reading of the followingdetailed description along with the accompanied drawings.

DETAILED DESCRIPTION OF THE INVENTION

The structure of a liquid crystal display apparatus according to thepresent invention will be explained with reference to FIGS. 1A to 1D.FIG. 1A is a cross-sectional view of a device substrate 101 beforesemiconductor device is pasted to the device substrate. FIG. 1B is a topsurface view of the device substrate 101 illustrated in FIG. 1A. FIG. 1Ais a cross-sectional view of the device substrate 101 illustrated inFIG. 1B taken along the line A-A′.

The device substrate 101 illustrated in FIGS. 1A and 1B has a concaveportion 102. One or a plurality of LED 103 is provided in the concaveportion 102. The concave portion 102 can be formed by a known means, forexample, a mold. The driving of the LED 103 is controlled by a thin filmcircuit (hereinafter, LED driver thin film circuit) 104 for driving theLED 103. The LED driver thin film circuit 104 is not always necessary tobe provided in the concave portion 102, that is, the LED driver thinfilm circuit 104 can be provided except the concave portion 102. The wayof forming the LED driver thin film circuit 104 will be described later.

Reference numeral 105 denotes a wiring formed over the device substrate101. The wiring 105 connects electrically the LED 103 to the LED driverthin film circuit 104, and also connects electrically the LED driverthin film circuit 104 to a semiconductor device pasted later to anexterior of the liquid crystal display apparatus. The wiring 105 can beformed over the device substrate 101 by a known means such as plating.

Reference numeral 106 denotes a reflection film that is formed bydepositing metals by vapor deposition in the concave portion 102. Toprevent short-circuiting, the reflection film 106 is deposited to beelectrically separated from the wiring 105 or the LED 103. In thisembodiment, as a means for reflecting light emitted from the LED 103 inthe direction of a liquid crystal cell, a reflection film that is formedby vapor deposition is used, however, a reflection plate that is formedseparately may be pasted onto the device substrate 101. In this case,the reflection plate is preferably pasted onto the position so as toreflect light emitted from the LED 103 in the direction of a liquidcrystal cell. For instance, the reflection plate can be provided oversurface that is opposing to the LED 103 and that is not provided withthe concave portion 102.

The LED 103 is covered with a resin 107. In this embodiment, the resin107 fills the concave portion 102. In case that the LED driver thin filmcircuit 104 is provided in the concave portion 102, the LED driver thinfilm circuit 104 is covered with the resin 107. As the resin 107, knownresin such as acrylic resin, epoxy resin, urethane resin, polycarbonateresin, or vinyl resin can be used. Transparent particles havingdifferent refractive index from that of the resin can be dispersed inthe resin 107. For instance, spherical particles can be dispersed inpolymethyl methacrylate resin. It is desired that resin be appropriatelyselected according to the pasting process of a semiconductor device.

In FIGS. 1A and 1B, reference numeral 108 denotes a light source portionthat is provided with the LED 103 and the reflection film 106, and thatis covered with the resin 107.

FIG. 1C is a cross-sectional view of the liquid crystal displayapparatus according to the invention in which a semiconductor device ispasted and a liquid crystal cell is completed. FIG. 1D is a top view ofthe liquid crystal display apparatus illustrated in FIG. 1C. FIG. 1C isa cross-sectional view of FIG. 1D taken along the line of B-B′.

A semiconductor device 110 is pasted to the resin 107 by an adhesive109. Not shown in FIG. 1C, a first polarization plate is providedbetween the resin 107 and the adhesive 109. In this embodiment, as shownin FIGS. 1C and 1D, the semiconductor device 110 is not only used to apixel portion of a liquid crystal display apparatus but also used to athin film circuit 111 for driving or signal processing a liquid crystaldisplay apparatus.

Reference numeral 113 denotes a counter substrate that is encapsulatedwith liquid crystal 112 by a sealant 114. The region where the liquidcrystal 112 is encapsulated by the counter substrate 113 corresponds toa panel 115. Light from the light source portion 108 is radiated to apixel portion 116 provided to the panel 115. In addition, the thin filmcircuit 111 is electrically connected to the wiring 105 by wire bondingmethod, flip chip method, or the like.

According to this embodiment, signals or power source voltage can besupplied to a liquid crystal display apparatus via the wiring 105, butnot exclusively, signals or power source voltage may be supplied bylight using a light-emitting device, a light sensor, or the like, or byelectromagnetic induction using an antenna coil.

As a plastic substrate, ARTON® containing norbornene resin with polargroup by JSR Corporation can be used. In addition, a plastic substratesuch as polyethylene terephthalate (PET), polyether sulfone (PES),polyethylene naphthalate (PEN), polycarbonate (PC), nylon, polyetherether ketone (PEEK), polysulfone (PSF), polyetherimide (PEI),polyalylate (PAR), polybutylene terephthalate (PBT), or polyimide can beused.

An example that a concave portion is provided to a device substrate andan LED is provided in the concave portion is explained in thisembodiment, however, the invention is not limited thereto. A flatplastic substrate without concave portion can be used as the devicesubstrate.

A structure of the liquid crystal display apparatus that utilizes a flatplastic substrate as a device substrate will be explained with referenceto FIGS. 2A to 2D. FIG. 2A is a cross-sectional view of a devicesubstrate in which a semiconductor device has not pasted yet. The devicesubstrate 201 is flat and not provided with a concave portion. FIG. 2Bis a top view of the device substrate 201 illustrated in FIG. 2A. FIG.2A is a cross-sectional view of FIG. 2B taken along the line A-A′.

One or a plurality of LED 203 is provided over the device substrate 201illustrated in FIGS. 2A and 2B. Reference numeral 204 denotes an LEDdriver thin film circuit. The LED driver thin film circuit 204 iselectrically connected to the LED 203 by a wiring 205. The wiring 205 isused for electrically connecting the LED driver thin film circuit 204 ora semiconductor device, which is formed later, to exterior of the liquidcrystal display apparatus. To prevent short-circuiting, a reflectionfilm 206 is deposited to be separated from the wiring 205 and the LED203. A reflection film that is formed separately can be used instead ofthat formed by vapor deposition.

The LED 203 is covered with a resin 207. In this embodiment, aphotosensitive resin is coated and partly exposed, then, the resin 207is coated in order to expose a part of the wiring 205. The LED driverthin film circuit 204 may also be covered with the resin 207. In FIGS.2A and 2B, reference numeral 208 denotes a light source portion that isprovided with the LED 203 and the reflection film 206, and that iscovered with the resin 207.

FIG. 2C is a cross-sectional view of a liquid crystal display apparatusaccording to the invention in which a semiconductor device is pasted anda liquid crystal cell is completed. FIG. 2D is a top view of the liquidcrystal display apparatus illustrated in FIG. 2C. FIG. 2C is across-sectional view of FIG. 2D taken along the line of B-B′.

A semiconductor device 210 is pasted onto the resin 207 by an adhesive209. Not shown in FIG. 2C, a first polarization plate is providedbetween the resin 207 and the adhesive 209. In addition, referencenumeral 211 corresponds to a thin film circuit formed using thesemiconductor device 210.

Reference numeral 213 denotes a counter substrate that is encapsulatedwith liquid crystal 212 by a sealant 214. The region where the liquidcrystal 212 is encapsulated by the counter substrate 213 corresponds toa panel 215. Light from the light source portion 208 is radiated to apixel portion 216 provided with the panel 215. In addition, the thinfilm circuit 211 is electrically connected to the wiring 205 by wirebonding method, flip chip method, or the like.

The concave portion of the device substrate allows the LED to be coveredwith a resin while wiring is exposed by only dropping a resin into theconcave portion. Further, a reflection film in the concave portionallows light emitted from LED to radiate effectively to the pixelportion. In case that the concave portion is not provided, the intensityof the device substrate can be further increased compared with the casethat the concave portion is provided.

Then, a specific method for manufacturing a semiconductor device usedfor the thin film circuit and the liquid crystal display apparatus and away of pasting the semiconductor device onto the device substrate willbe explained hereinafter. In this embodiment, though two TFTs areexemplified as the semiconductor device, the semiconductor deviceincluded in a thin film circuit and a liquid crystal display apparatusis not limited to the two TFTs, any circuit device can be used. A memorydevice, a diode, a photoelectric conversion device, a resistive element,a coil, a capacitance element, an inductor, or the like can be typicallygiven as examples for the semiconductor device, in addition to TFTs.

As shown in FIG. 3A, a metal film 501 is deposited over a firstsubstrate 500 by sputtering. Here, tungsten is used for forming themetal film 501 and formed to have a thickness of from 10 to 200 nm,preferably, from 50 to 75 nm. In this embodiment, the metal film 501 isdeposited directly on the first substrate 500, but the metal film 501may also be deposited after covering the first substrate 500 by aninsulating film such as silicon oxide, silicon nitride, siliconoxynitride, or the like.

An oxide film 502 is deposited to be stacked after depositing the metalfilm 501 without exposing to the air. A silicon oxide film is depositedto have a thickness of from 150 to 300 nm as the oxide film 502. In caseof depositing by sputtering, a film is deposited over the edge of thefirst substrate 500. Hence, the metal film 501 and the oxide film 502are preferably removed selectively by O₂ ashing and the edge of thefirst substrate 500 is preferably cut by dicing to prevent the oxidefilm 502 from remaining over the first substrate 500 in separating in alater process.

In depositing the oxide film 502, pre-sputtering, that is, plasma isgenerated by shielding between a target and a substrate with shutter, iscarried out as a preliminary step toward sputtering. The first substrate500 is pre-sputtered under the equilibrium state, that is, Ar flow rateused is 10 sccm; O₂, 30 sccm; substrate temperature, 270° C.; anddeposition power, 3 kW. A metal oxide film 503 is deposited having anultra thin thickness of several nm (here, 3 nm) between the metal film501 and the oxide film 502 by the pre-sputtering. The metal oxide film503 is formed by oxidization of the metal film 501. Hence, the metaloxide film 503 is formed of tungsten oxide.

The metal oxide film 503 is, but not exclusively, deposited bypre-sputtering in this embodiment. For example, the metal oxide film 503may be deposited by oxidizing deliberately the surface of the metal film501 in plasma using oxygen or oxygen added with inert gases such as Aror the like.

After depositing the oxide film 502, a base film 504 is deposited byplasma chemical vapor deposition (hereinafter, PCVD). Here, a siliconoxynitride film is deposited to have a thickness approximately of 100 nmas the base film 504. After depositing the base film 504, asemiconductor film 505 is deposited without exposing to the atmosphere.The semiconductor film 505 is formed to have a thickness of from 25 to100 nm, preferably, from 30 to 60 nm. The semiconductor film 505 may beeither an amorphous semiconductor or a polycrystalline semiconductor.The semiconductor film may be formed by not only silicon but alsosilicon germanium. In case of using silicon germanium, the concentrationof germanium is preferably approximately from 0.01 to 4.5 atomic %.

As shown in FIG. 3B, the semiconductor film 505 is crystallized by aknown technique. As the known technique, thermal crystallization usingan electric heating furnace, laser crystallization using a laser light,and ramp annealing crystallization using an infrared light.Alternatively, crystallization using catalytic elements can be usedaccording to the technique disclosed in Unexamined Patent PublicationNo. 7-130652.

The semiconductor film 505 that is a polycrystalline semiconductor filmmay be formed in advance by sputtering, PCVD, or thermal CVD.

The semiconductor film 505 is crystallized by laser crystallization inthis embodiment. A crystal having a large grain diameter can be obtainedby laser light irradiation of from a second harmonic to a fourthharmonic of a fundamental wave by using a solid laser capable ofcontinuously oscillating. Typically, a second harmonic (532 nm) or athird harmonic (355 nm) of Nd: YVO₄ laser (fundamental wave of 1064 nm)may be applied. When a continuously oscillating laser is used, a laserlight emitted from the continuously oscillating YVO₄ laser having anoutput power of 10 W is converted to a harmonic by a nonlinear opticaldevice. There is also a method in which a harmonic is outputted by usingnonlinear optical device. Preferably, the laser light is formed by usingan optical system such that it becomes in a rectangular shape or anelliptical shape on an irradiating face and radiated to thesemiconductor film 505. The laser irradiation is carried at energydensity of approximately from 0.01 to 100 MW/cm² (preferably from 0.1 to10 MW/cm²) and a scanning speed of approximately from 10 to 2000 cm/s.

The laser crystallization may be carried out by radiating a continuouswave laser light of fundamental wave and a continuous wave laser lightof harmonic wave, or radiating a continuous wave laser light offundamental wave and a pulsed laser light of harmonics.

A laser light may be radiated in an inert gas atmosphere such as raregas or nitride. According to this, the surface roughness of asemiconductor due to a laser irradiation, further, the variations of athreshold value due to the variations of interface state density can beprevented.

A semiconductor film 506 that is enhanced its degree of crystallinity isformed by irradiating the above described semiconductor film 505 with alaser light. Next, as shown in FIG. 3C, the semiconductor film 506 ispatterned to form island like semiconductor films 507, 508. Varioussemiconductor devices as typified by TFTs are formed using the islandlike semiconductor films 507, 508. In this embodiment, the base film 504and the island like semiconductor films 507, 508 are in contact witheach other, but an electrode, an insulating film, or the like may beformed between the base film 504 and the island like semiconductor films507, 508 depending on a semiconductor device. For example, in case of abottom gate type TFT that is one of the semiconductor devices, a gateelectrode and a gate insulating film are formed between the base film504 and the island like semiconductor films 507, 508.

In this embodiment, top gate type TFTs 509 and 510 are formed using theisland like semiconductor films 507, 508 (FIG. 3D). Specifically, a gateinsulating film 511 is deposited so as to cover the island likesemiconductor films 507, 508. Then, a conductive film is deposited overthe gate insulating film 511 and patterned, and gate electrodes 512, 513are formed. Next, impurities imparting n-type are added to the islandlike semiconductor films 507, 508 using the gate electrodes 512, 513 orresist that is deposited and patterned as masks to form a source region,a drain region, and an LDD (Lightly Doped Drain) region. Here, TFTs 509,510 are n-type, in case of using p-type TFTs, impurities impartingp-type are added.

According to the above described process, TFTs 509, 510 can be formed. Amethod for manufacturing the TFTs is not limited to the above describedprocess.

A first interlayer insulating film 514 is fabricated so as to cover theTFTs 509, 510. Contact holes are formed at the gate insulating film 511and the first interlayer insulating film 514, and terminals 515 to 518connected to the TFTs 509, 510 via the contact holes are formed so as tobe in contact with the first interlayer insulating film 514.

A pixel electrode 540 of a liquid crystal cell is formed by atransparent conductive film such as ITO so as to be in contact with theterminal 515. Then, an orientation film 541 is formed to cover the pixelelectrode 540, and rubbing treatment is carried out to the orientationfilm 541. A part of the terminal 518 is exposed by etching or the likeso as not to be covered by the orientation film 541.

A protective layer 521 is formed over the orientation film 541. As amaterial for forming the protective layer 521, a material which canprotect the surface of the TFTs 509, 510, the orientation film 541, andterminals 515 to 518 in pasting or separating the second substrate in alater process, and which can be removed after separating a secondsubstrate is used. For example, the protective film 521 can be formed bycoating resin of epoxy series, acrylate series, or silicon series thatis soluble in water over the whole surface, and baking.

In this embodiment, a water-soluble resin (TOAGOSEI Co., Ltd.:VL-WSHL10) is spin-coated to have a thickness of 30 μm, and exposed fortwo minutes to be partially cured, then, exposed its back with UV raysfor 2.5 minutes, and then, exposed its surface for 10 minutes, that is,12.5 minutes in total, to be fully cured. Consequently, the protectivelayer 521 is formed (FIG. 3E).

Though an example that the protective layer 521 is formed after theorientation film 541 is formed is explained in this embodiment, theorientation film 541 may be formed after removing the protective layer521 in a later process. However, in case of stacking a plurality oforganic resins, there is a threat of melting the stacked organic resindepending on the solvent in coating or baking, or increasing excessivelyits density. In case of forming the protective layer 521 after formingthe orientation film 541, each of which is formed by organic resinsoluble in the same etchant, an inorganic insulating film (a SiN_(X)film, a SiN_(X)O_(Y) film, an AlN_(X) film, or an AlN_(X)O_(Y) film) ispreferably formed so as to cover the first interlayer insulating film514, and be disposed between the first interlayer insulating film 514and the terminals 515 to 518 for removing smoothly the protective film521 in a later process.

For separating smoothly in a later process, the metal oxide film 503 iscrystallized. By this crystallization, the metal oxide film 503 becomessusceptible to fracture in grain boundary and enhanced its brittleness.The crystallization is carried out by heat-treating for approximately atfrom 420 to 550° C. for from 0.5 to 5 hours.

Then, some treatments are carried out on the metal oxide film 503 inorder to make it easier for the metal oxide film 503 to be separated byweakening partly the adhesiveness between the metal oxide film 503 andthe oxide film 502 or the adhesiveness between the metal oxide film 503and the metal film 501. Specifically, the periphery of the region thatis to be separated is locally pressed from outside to be damaged a partof the inside or the boundary face-neighborhood of the oxide film 503.Specifically, a hard needle such as a diamond pen is attachedperpendicular to the edge-neighborhood of the metal oxide film 503 andmoved along with the metal oxide film 503 with applying loading.Preferably, a scriber device can be used to move with applying loadingon the region with press force ranging from 0.1 to 2 mm. It is importantto carry out some treatment for easy separating, that is, it isimportant to prepare for separating process. Such preparatory process toweaken selectively the adhesiveness will prevent poor separating andimprove the process yield.

Next, a second substrate 523 is pasted onto the protective film 521 witha two-sided tape 522, and a third substrate 525 is pasted over the firstsubstrate 500 with a two-sided tape 524 (FIG. 4A). An adhesive can beused instead of a two-sided tape. For example, it is possible to reducethe load of a semiconductor device, which becomes increased byseparating the second substrate, by using an adhesive that is meltedwith UV light.

The third substrate 525 prevents the first substrate 500 from beingdamaged in a later process for separating. For the second substrate 523and the third substrate 525, the substrate that has higher rigidity thanthat of the first substrate 500, for example, a quartz substrate or asemiconductor substrate is preferably to be used.

Then, the metal film 501 is separated from the oxide film 502 by aphysical means. The separation of metal film 501 is started from theregion that is partly weakened its adhesiveness to the metal film 501 orthe oxide film 502 in the previous process.

The metal film 501 may be removed by separating the metal film 501 frommetal oxide film 503, by separating the oxide film 502 from the metaloxide film 503, or splitting the metal oxide film 503 into two. Further,the second substrate 523 to which semiconductor devices (here, TFTs 509,510) are pasted is separated from the third substrate 525 to which thefirst substrate 500 and the metal film 501 are pasted. The separationcan be carried out with comparatively small force (for example, man'shand, air pressure of gas sprayed from a nozzle, ultrasonic waves, orthe like). FIG. 4B shows a state of after separating.

A first polarization plate 527 provided over a resin 533 is bonded tothe oxide layer 502 that is partly attached with the metal oxide film503 with an adhesive 526 (FIG. 4C). At this time, it is important thatthe material for the adhesive 526 is selected in order that theadhesiveness between the oxide layer 502 and the first polarizationplate 527 by the adhesive 526 to be stronger than that between thesecond substrate 523 and the protective layer 521 by the two-sided tape522.

If the metal oxide film 503 is remained over the surface of the oxidefilm 502, the adhesiveness of the polarization plate 527 may get worse,so that the remained metal oxide film may be completely removed beforebonding to the oxide film 502.

In case of using the semiconductor devices 509, 510 are used for thethin film circuit, the semiconductor devices 509, 510 are unnecessary tobe pasted to overlap with the first polarization plate 527.

As the adhesive 526, various curing adhesives such as a photo-curingadhesive, for example, a reaction-curing adhesive, a thermal-curingadhesive, or a UV-curing adhesive, or an anaerobic adhesive can be used.More preferably, the adhesive 526 is given high thermal conductivity bymeans of mixing powder comprising silver, nickel, aluminum, or aluminumnitride, or filler.

In addition, reference numeral 530 denotes a wiring formed over thedevice substrate 534. The wiring 530 is formed by coating copper withsolder, gold, or tin.

As shown in FIG. 5A, the two-sided tape 522 and the second substrate 523are separated sequentially or simultaneously from the protective layer521. The two-sided tape 522 can be separated simultaneously with curingthe adhesive 526 by using UV-curing adhesive as the adhesive 526, and byusing a tape or adhesive that is separated by UV light as the two-sidedtape 522.

As shown in FIG. 5B, the protective film 521 is removed by water sincethe protective film 521 is formed by a resin that is soluble in water.In case that the remained protective film 521 causes deterioration, theremained protective film 521 is preferably removed by carrying outcleaning treatment or O₂ plasma treatment to the surface.

In this embodiment, tungsten is used for a material of the metal film501, however, the present invention is not limited thereto. Any materialcan be used as long as which includes metals that allows a substrate tobe separated by forming the metal oxide film 503 over the surface of thematerial and crystallizing the metal oxide film 503. For instance, TiN,WN, Mo, or the like can be used in addition to tungsten. In case ofusing these alloys as the metal film, the optimal temperature for heattreatment to crystallize differs depending on the composition ratio ofthe metal film. On the basis of the fact, the heat treatment can becarried out at the temperature that has no adverse effects on themanufacturing process for a semiconductor device, and selection rangesof the manufacturing process become difficult to be restricted byadjusting the composition ratio of the metal film.

A liquid crystal cell is formed as illustrated in FIG. 6.

After the protective layer 521 is formed, a counter substrate 542 thatis formed separately is pasted with sealant 543. Filler may be mixedinto the sealant. The counter substrate 542 has a thickness ofapproximately several hundreds μm, and is provided with a counterelectrode 543 formed by a transparent conductive film and an orientationfilm 544 that is rubbing treated. In addition, a color filter and ablack matrix (a shielding film) to prevent disclination may be formed.Further, a second polarization plate 545 is pasted onto the oppositeside of the counter electrode 543 on which the counter substrate 542 isformed.

Then, liquid crystal 546 is injected and encapsulated to complete apanel 550. In addition, the way of injecting liquid crystal may bedispenser method or dip method. A spacer may be provided between thepixel electrode 540 and the counter electrode 543 for keeping cell gaps.The liquid crystal display apparatus is completed by connectingelectrically the terminal 518 to the wiring 530 provided with the devicesubstrate 534 by wire bonding method.

Then, a method for manufacturing a liquid crystal display apparatusaccording to the invention, which is different from that illustrated inFIGS. 3 to 6, will be explained. In this embodiment, though a TFT isexemplified as the semiconductor device, the semiconductor deviceincluded in a thin film circuit and a liquid crystal display apparatusis not limited to the TFT, any circuit device can be used. For example,a memory device, a diode, a photoelectric conversion device, a resistiveelement, a coil, a capacitance element, an inductor, or the like can betypically given, in addition to TFTs.

As shown in FIG. 7A, a metal film 1501 is deposited over a firstsubstrate 1500 by sputtering. Here, tungsten is used for forming themetal film 1501 and formed to have a thickness of from 10 to 200 nm,preferably, from 50 to 75 nm. In this embodiment, the metal film 1501 isdeposited directly on the first substrate 1500, but the metal film 1501may also be deposited after covering the first substrate 1500 by aninsulating film such as silicon oxide, silicon nitride, siliconoxynitride, or the like.

An oxide film 1502 composing the insulating film is deposited to bestacked after depositing the metal film 1501 without exposing to theair. A silicon oxide film is deposited to have a thickness of from 150to 300 nm as the oxide film 1502. In case of depositing by sputtering, afilm is deposited over the edge of the first substrate 1500. Hence, themetal film 1501 and the oxide film 1502 are preferably removedselectively by O₂ ashing to prevent the oxide film 1502 from remainingover the first substrate 1500 in separating in a later process.

In depositing oxide film 1502, pre-sputtering, that is, plasma isgenerated by shielding between a target and a substrate with shutter, iscarried out as a preliminary step toward sputtering. The first substrate1500 is pre-sputtered under the equilibrium state, that is, Ar flow rateused is 10 sccm; O₂, 30 sccm; substrate temperature, 270° C.; anddeposition power, 3 kW. A metal oxide film 1503 is deposited having anultra thin thickness of several nm (here, 3 nm) between the metal film1501 and the oxide film 1502 by the pre-sputtering. The metal oxide film1503 is formed by oxidization of the metal film 1501. Hence, the metaloxide film 1503 is formed of tungsten oxide.

The metal oxide film 1503 is, but not exclusively, deposited bypre-sputtering in this embodiment. For example, the metal oxide film1503 may be deposited by oxidizing deliberately the surface of the metalfilm 1501 in plasma using oxygen or oxygen added with inert gases suchas Ar or the like.

After depositing the oxide film 1502, a base film 1504 composing theinsulating film is deposited by PCVD. Here, a silicon oxynitride film isdeposited to have a thickness of approximately 100 nm as the base film1504. After depositing the base film 1504, a semiconductor film 1505 isdeposited without exposing to the atmosphere. The semiconductor film1505 is formed to have a thickness of from 25 to 100 nm, preferably,from 30 to 60 nm. The semiconductor film 1505 may be either an amorphoussemiconductor or a polycrystalline semiconductor. The semiconductor filmmay be formed by not only silicon but also silicon germanium. In case ofusing silicon germanium, the concentration of germanium is preferablyapproximately from 0.01 to 4.5 atomic %.

Next, the semiconductor film 1505 is crystallized by a known technique.As the known technique, thermal crystallization using an electricheating furnace, laser crystallization using a laser light, and rampannealing crystallization using an infrared light. Alternatively,crystallization using catalytic elements can be used according to thetechnique disclosed in Unexamined Patent Publication No. 7-130652.

The semiconductor film 1505 is crystallized by laser crystallization inthis embodiment. Before the laser crystallization, the semiconductorfilm is thermal-annealed at 500° C. for 1 hour to increase resistance ofthe semiconductor film to laser. In this embodiment, the heat treatmentenhances the brittleness of the metal oxide film 1503 to make it easierfor the first substrate 1500 to be separated later. By thiscrystallization, the metal oxide film 1503 becomes susceptible tofracture in grain boundary and enhanced its brittleness. Thecrystallization of the metal oxide film 1503 is preferably carried outby heat-treating for approximately at from 420 to 550° C. from 0.5 to 5hours.

A crystal having a large grain diameter can be obtained by laser lightirradiation of from a second harmonic to a fourth harmonic of afundamental wave by using a solid laser capable of continuouslyoscillating. Typically, a second harmonic (532 nm) or a third harmonic(355 nm) of Nd: YVO₄ laser (fundamental wave of 1064 nm) may be applied.When a continuously oscillating laser is used, a laser light emittedfrom the continuously oscillating YVO₄ laser having an output power of10 W is converted to a harmonic by a nonlinear optical device. There isalso a method in which a harmonic is outputted by using a nonlinearoptical device. Preferably, the laser light is formed by using anoptical system such that it becomes in a rectangular shape or anelliptical shape when radiated to an irradiating face, and radiated tothe semiconductor film 1505. On this occasion, an energy density ofapproximately from 0.01 to 100 MW/cm² (preferably from 0.1 to 10 MW/cm²)is necessary and a semiconductor film may be irradiated with the laserlight while it is moved relatively thereto at a speed of approximatelyfrom 10 to 2000 cm/s.

The laser crystallization may be carried out by radiating a continuouswave laser light of fundamental wave and a continuous wave laser lightof harmonic wave, or radiating a continuous wave laser light offundamental wave and a pulsed laser light of harmonics.

A laser light may be radiated in the inert gas atmosphere such as raregas or nitride. According to this, the surface roughness of asemiconductor due to a laser irradiation, further, the variations of athreshold value due to the variations of interface state density can beprevented.

The crystallinity of the semiconductor film 1505 is further enhanced bythe above described crystallization. The semiconductor film 1505 that isa polycrystalline semiconductor film may be formed in advance bysputtering, PCVD, thermal CVD, or the like.

Next, as shown in FIG. 7B, the semiconductor film 1505 is patterned toform island like semiconductor films 1507, 1508. Various semiconductordevices as typified by TFTs are formed using the island likesemiconductor films 1507, 1508. In this embodiment, the base film 1504and the island like semiconductor films 1507, 1508 are in contact witheach other, but an electrode, an insulating film, or the like may beformed between the base film 1504 and the island like semiconductorfilms 1507, 1508 depending on a semiconductor device. For example, incase of a bottom gate type TFT that is one of the semiconductor devices,a gate electrode and a gate insulating film are formed between the basefilm 1504 and the island like semiconductor films 1507, 1508.

In this embodiment, top gate type TFTs 1509, 1510 are formed using theisland like semiconductor films 1507, 1508 (FIG. 7C). Specifically, agate insulating film 1511 is deposited so as to cover the island likesemiconductor films 1507, 1508. Then, a conductive film is depositedover the gate insulating film 1511 and patterned, and then, gateelectrodes 1512, 1513 are formed. Next, impurities imparting n-type areadded to the gate electrodes 1507, 1508 using the gate electrodes 1512,1513 or resist that is deposited and patterned as masks to form a sourceregion, a drain region, and an LDD (Lightly Doped Drain) region. Here,TFTs 1509, 1510 are n-type, but impurities imparting p-type are added incase of using p-type TFTs.

According to the above described process, TFTs 1509, 1510 can be formed.A method for manufacturing the TFTs is not limited to the abovedescribed process.

A first interlayer insulating film 1514 is fabricated so as to cover theTFTs 1509, 1510. Contact holes are formed in the gate insulating film1511 and the first interlayer insulating film 1514, and terminals 1515to 1518 connected to the TFTs 1509, 1510 via the contact holes areformed so as to be in contact with the first interlayer insulating film1514.

The TFT 1510 used as a switching element of the pixel portion of theliquid crystal display apparatus is electrically connected to theterminal 1518. A pixel electrode of a liquid crystal cell is formed bytransparent conductive film such as ITO so as to connect to the terminal1518. A spacer 1519 is formed by using an insulating film. Then, anorientation film 1520 is formed to cover the pixel electrode 1550, theterminal 1518, and the spacer 1519, and rubbing treatment is carried outthereto. In addition, the orientation film 1520 may be formed to overlapwith the thin film circuit.

Then, a sealant 1521 is formed to encapsulate liquid crystal. As shownin FIG. 8A, liquid crystal 1522 is dropped in the region encircled bythe sealant 1521. A counter substrate 1523 that is formed separately ispasted with sealant 1521. FIG. 8B is a view showing a state after thecounter substrate 1523 is pasted. Filler may be mixed into the sealant1521. The counter substrate 1523 has a thickness of approximatelyseveral hundreds μm, and is provided with a counter electrode 1524formed by a transparent conductive film and an orientation film 1526that is rubbing treated. In addition, a color filter and a black matrix(a shielding film) to prevent disclination may be formed. Further, asecond polarization plate 1527 is pasted onto the opposite side of thecounter electrode 1524 on which the counter substrate 1523 is formed.

The region where the counter electrode 1524, the liquid crystal 1522,and the pixel electrode 1550 are overlapped each other corresponds to aliquid crystal cell 1528. When the liquid crystal cell 1528 iscompleted, a panel 1529 is also completed. In addition, though a thinfilm circuit 1530 is not overlapped with the counter substrate 1523, thethin film circuit 1530 may dare to be overlapped with the countersubstrate 1523. In this case, a resin may be filled between the countersubstrate and the thin film circuit to increase mechanical strength of aliquid crystal display apparatus.

In this embodiment, the liquid crystal is encapsulated by dispensermethod (dropping method) though, the invention is not limited thereto.The liquid crystal may be encapsulated by dipping method (pumpingmethod) utilizing capillary phenomenon after pasting the countersubstrate onto the liquid crystal.

Next, as shown in FIG. 9A, a protective film 1531 is formed to cover thethin film circuit 1530 and the panel 1529. The protective layer 1531 isformed by a material that can protect the thin film circuit 1530 and thepanel 1529 in pasting or separating a second substrate 1533 later, andthat can be removed after separating the second substrate 1533. Forexample, the protective film 1531 can be formed by coating resin ofepoxy series, acrylate series, or silicon series that is soluble inwater over the whole surface.

In this embodiment, a water-soluble resin (TOAGOSEI Co., Ltd.:VL-WSHL10) is spin-coated to have a thickness of 30 μm, and exposed fortwo minutes to be partially cured, then, exposed its back with UV raysfor 2.5 minutes, and then, exposed its surface for 10 minutes to befully cured. Consequently, the protective layer 1531 is formed.

In case of stacking a plurality of organic resins, there is a threat ofmelting the stacked organic resin depending on the solvent in coating orbaking, or increasing excessively its density. In case of formingsimultaneously both the first interlayer insulating film 1514 and theprotective layer 1531, each of which is formed by organic resin solublein the same etchant, an inorganic insulating film (a SiN_(X) film, aSiN_(X)O_(Y) film, an AlN_(X) film, or an AlN_(X)O_(Y) film) ispreferably formed so as to cover the first interlayer insulating film1514.

Then, some treatments are carried out on the metal oxide film 1503 inorder to make it easier for the metal oxide film 1503 to be separated byweakening partly the adhesiveness between the metal oxide film 1503 andthe oxide film 1502 or the adhesiveness between the metal oxide film1503 and the metal film 1501. Specifically, the periphery of the regionthat is to be separated is locally pressed from outside to damage a partof the inside or the boundary face-neighborhood of the oxide film 1503.Specifically, a hard needle such as a diamond pen is attachedperpendicular to the edge-neighborhood of the metal oxide film 1503 andmoved along with the metal oxide film 1503 with applying loading.Preferably, a scriber device can be used to move with applying loadingon the region with press force ranging from 0.1 to 2 mm. It is importantto carry out some treatment for easy separating, that is, it isimportant to prepare for separating. Such preparatory process to weakenselectively the adhesiveness will prevent poor separating and improvethe process yield.

Next, a second substrate 1533 is pasted onto the protective layer 1531with a two-sided tape 1532, and a third substrate 1535 is pasted overthe first substrate 1500 with a two-sided tape 1534. An adhesive can beused instead of a two-sided tape. For example, it is possible to reducethe load of a semiconductor device, which is increased by separating thesecond substrate, by using an adhesive that is melted with UV light. Thethird substrate 1535 prevents the destruction of the first substrate1500 in the subsequent process of separating. For the second substrate1533 and the third substrate 1535, the substrate that has higherrigidity than that of the first substrate 1500, for example, a quartzsubstrate or a semiconductor substrate is preferably to be used.

Then, the metal film 1501 is separated from the oxide film 1502 by aphysical means. The separation of metal film 1501 is started from theregion that is partly weakened its adhesiveness with respect to themetal film 1501 or the oxide film 1502 in the previous process.

Three separating portions may be resulted from the separation of metalfilm 1501, that is, the separating portion of the metal film 1501 andmetal oxide film 1503, the separating portion of the oxide film 1502 andthe metal oxide film 1503, or the separating portion within the metaloxide film 1503. Further, the second substrate 1533 on whichsemiconductor devices (here, TFTs 1509, 1510) are pasted is separatedfrom the third substrate 1535 on which the first substrate 1500 and themetal film 1501 are pasted. The separation can be carried out withcomparatively small force (for example, man's hand, air pressure of gassprayed from a nozzle, ultrasonic waves, or the like). FIG. 9B shows astate of after the separating process.

A device substrate 1540 is bonded with an adhesive 1539 to the oxidelayer 1502 that is partly attached with the metal oxide film 1503 (FIG.10). At this time, it is important that the material for the adhesive1539 is selected in order that the adhesiveness to be stronger betweenthe oxide layer 1502 and the device substrate 1540 by the adhesive 1539than that between the second substrate 1533 and the protective layer1531 by the two-sided tape 1532.

As the adhesive 1539, various curing adhesives such as a photo-curingadhesive, for example, a reaction-curing adhesive, a thermal-curingadhesive, or a UV-curing adhesive, or an anaerobic adhesive can be used.More preferably, the adhesive 1539 is given high thermal conductivity bymeans of mixing powder comprising silver, nickel, aluminum, or aluminumnitride, or filler.

If the metal oxide film 1503 is remained over the surface of the oxidefilm 1502, the adhesiveness of the device substrate 1540 may get worse,so that the remained metal oxide film may be completely removed byetching or the like before bonding to a printed wiring board.

As shown in FIG. 10, the two-sided tape 1532 and the second substrate1533 are separated sequentially or simultaneously from the protectivelayer 1531. The two-sided tape 1532 can be separated simultaneously withcuring the adhesive 1539 by using UV-curing adhesive as the adhesive1539, and by using a tape or adhesive that is separated by UV light asthe two-sided tape 1532.

As shown in FIG. 11A, the protective film 1531 is removed by water sincethe protective film 1531 is formed by a resin that is soluble in water.In case that the remained protective film 1531 causes deterioration, theremained protective film 1531 is preferably removed by carrying outcleaning treatment or O₂ plasma treatment to the surface.

A terminal 1518, a wiring 1551 provided with the device substrate 1540are electrically connected each other by a wiring 1552 by wire bondingmethod, and a liquid crystal display apparatus is completed. The wiring1551 is completed, for example, by coating copper with gold or tin. Inaddition, a timing for connecting the terminal 1518 and the wiring 1551is not limited to the above described one.

It can be considered that a liquid crystal display apparatus iscompleted in this state. However, according to this embodiment,mechanical strength of the liquid crystal display apparatus is enhancedby encapsulating the liquid crystal display apparatus by a sealingmember.

As shown in FIG. 11B, the thin film circuit 1530 and the panel 1529 arecovered with a resin 1542 and a cover member 1543 is provided to protectthe thin film circuit 1530 and the panel 1529. In addition, the covermember 1543 is not always necessary to be provided, the device substrate1540 can be covered directly with a sealing member.

As material for the sealing member used for encapsulating the liquidcrystal display apparatus, a material that is used in general can beused. For instance, polymeric material such as polyester, acrylic acid,polyvinyl acetate, propylene, chloroethene, acrylonitrilebutadienestyrene resin, or polyethylene terephthalate can be used. The pixelportion of the liquid crystal display apparatus is exposed, or amaterial for the resin 1542 or a cover member 1543 is appropriatelyselected in encapsulating in order to pass light therethrough.

By encapsulating a liquid crystal display apparatus with a sealingmember, mechanical strength of the liquid crystal display apparatus isenhanced, heat generated in the liquid crystal display apparatus isradiated, and electromagnetic noises from adjacent circuit of externalof the liquid crystal display apparatus can be rejected.

A plastic substrate can be used for the device substrate 1540, the covermember 1543, and the counter substrate 1523. As a plastic substrate,ARTON® containing norbornene resin with polar group by JSR Corporationcan be used. In addition, a plastic substrate such as polyethyleneterephthalate (PET), polyether sulfone (PES), polyethylene naphthalate(PEN), polycarbonate (PC), nylon, polyether ether ketone (PEEK),polysulfone (PSF), polyetherimide (PEI), polyalylate (PAR), polybutyleneterephthalate (PBT), or polyimide can be used. It is desired that thedevice substrate 1540 has high thermal conductivity of approximatelyfrom 2 to 30 W/mK to radiate heat generated in the liquid crystaldisplay apparatus.

In this embodiment, tungsten is used for a material of the metal film1501, however, the present invention is not limited thereto. Anymaterial can be used as long as which includes metals that allows asubstrate to be separated by forming the metal oxide film 1503 over thesurface of the material and crystallizing the metal oxide film 1503. Forinstance, TiN, WN, Mo, or the like can be used in addition to tungsten.In case of using these alloys as the metal film, the optimal temperaturefor heat treatment to crystallize differs depending on the compositionratio of the metal film. On the basis of the fact, the heat treatmentcan be carried out at the temperature that has no adverse effects on themanufacturing process for a semiconductor device, and selection rangesof the manufacturing process become difficult to be restricted byadjusting the composition ratio of the metal film.

In addition, a semiconductor device used for an LED driver thin filmcircuit can be formed according to the above described method forforming a semiconductor device.

A material for a resin covering a light-emitting diode is preferably andappropriately selected depending on the method for curing a firstsubstrate, a second substrate, and an adhesive.

An example that a wiring formed over a device substrate is electricallyconnected to a thin film circuit or an LED driver thin film circuit byflip chip method instead of wire bonding method will be explainedhereinafter.

FIG. 12A is a cross-sectional view of a thin film circuit or an LEDdriver thin film circuit, each of which is provided with solder balls.

As shown in FIG. 12A, a semiconductor device 301 is electricallyconnected to a wiring over a device substrate with a solder ball 302.The solder ball 302 is provided to the side of the device substrate ofthe semiconductor device 301 and connected to an electrode 303 that iselectrically connected to the semiconductor device 301. The electrode303 may be formed by a conductive film that is the same as that of agate electrode of a TFT in case that the semiconductor device is theTFT.

FIG. 12B is a cross-sectional view of the thin film circuit or the LEDdriver thin film circuit in which semiconductor devices are stacked byflip chip method. As shown in FIG. 12B, semiconductor devices 310 and311, each of which is provided to two layers, are stacked. A wiringprovided to a device substrate is electrically connected to thesemiconductor device 310 with a solder ball 312. In addition, thesemiconductor device 310 is electrically connected to the semiconductordevice 311 with a solder ball 313.

FIG. 12C is a view showing an example that a wiring formed over a devicesubstrate is connected to a solder ball. As shown in FIG. 12C, a solderball 312 is connected to a wiring 321 directly connected to asemiconductor device 320.

In addition, flip chip method is effective for the case that the numberof connections between a thin film circuit or an LED driver thin filmcircuit and a wiring is large, since a pitch between wirings can berelatively reserved large compared with wire bonding method.

A solder ball and a wiring over a device substrate can be connected byvarious methods such as thermo-compression bonding andthermo-compression bonding with vibrations from ultrasonic wave. Anunder fill may fill interspace of thermo-compressed solder balls betweeneach other to improve the mechanical strength of connection portions orthe efficiency of radiation of heat generated in a thin film circuit. Anunder fill is not always necessary to be used, but it can prevent poorconnection due to stress occurred by mismatch of coefficient of thermalexpansion of a device substrate and a semiconductor device. Thecompression by applying ultrasonic wave can prevent poor connectioncompared with compression without ultrasonic wave. Especially, it iseffective for the case that the number of bumps used for connecting isat least approximately 300.

A wiring formed over a device substrate can be electrically connected toa thin film circuit or an LED driver thin film circuit in various formsby combining the ways described with reference to FIGS. 12A to 12C. Inaddition, a flip chip method and wire bonding method can be combined forconnecting.

An active matrix liquid crystal display apparatus is explained in thisembodiment though, a passive matrix liquid crystal display apparatus canbe adopted in the invention.

According to above described structure of the invention, a liquidcrystal display apparatus can be drastically reduced its thickness andweight without being damaged the mechanical strength. Applying a liquidcrystal display apparatus according to the invention to an electronicappliance, a space for using IC can be kept large and an electronicappliance can be sophisticated without preventing the electronicappliance from being lightweight and downsized. Especially, a liquidcrystal display apparatus according to the present invention is usefulfor a portable electronic appliance since usability thereof becomesimproved by reducing the weight and the size. According to theinvention, even when size of a pixel portion of a liquid crystal displayapparatus is increased, weight thereof is almost the same as that of aliquid crystal display apparatus using a conventional glass substrate.

EXAMPLES

Hereinafter, examples of the present invention will be explained.

Example 1

The case that the present invention is applied to a card as typified byan electronic card will be explained in this example.

The configuration of an electronic card according to this example willbe explained with reference to FIGS. 13A to 13D. FIG. 13A is across-sectional view showing a device substrate 401 at the time that apanel is completed. FIG. 13B is a top surface view of the devicesubstrate illustrated in FIG. 13A. FIG. 13A shows the state that istaken along the line of A-A′.

The device substrate 401 illustrated in FIGS. 13A and 13B has a concaveportion 402 in which an LED 403 or a plurality of those is formed. AnLED driver thin film circuit 404 is provided to the concave portion 402.The LED 403 and the LED driver circuit are covered with a resin 407.

Reference numeral 415 denotes a panel, and 411 denotes a thin filmcircuit. The panel and the thin film circuit are formed separately andpasted onto the device substrate 401. The thin film circuit 411 has anantenna coil 406. A wiring 405 formed over the device substrate 401 isconnected electrically to the antenna coil 406.

FIG. 13C is a cross-sectional view of a liquid crystal display apparatusaccording to the invention at the time of completing an electronic card.FIG. 13D is a top view showing a liquid crystal display apparatusillustrated in FIG. 13C. FIG. 13C is a cross-sectional view showing FIG.13D taken along the line B-B′.

An electronic card as illustrated in FIGS. 13C and 13D is covered with acover member 420 so as to seal the panel 415 and the thin film circuit411 formed over the device substrate with a resin 422. In thisembodiment, light emitted from the panel 415 is transmitted through aportion 421, but not exclusively, the cover member can be formed of amaterial that is transparent to light in order that light emitted frompanel 415 also passes through the area except the portion 421.

In this embodiment, the structure of an electronic card that suppliessignal or power supply voltage by electromagnetic introduction using anantenna coil is explained, however, the electronic card can have thestructure that supplies signal or power supply voltage by light using alight-emitting device or light sensor. Further, the electronic card isnot limited to a noncontact card. The electronic card may be a contactcard that transmits directly signals to a terminal device via aterminal.

The electronic card can be used for various purposes such as a cashcard, a credit card, a prepaid card, an ID card used for identification,and a commuter pass. If an electronic card is installed with the liquidcrystal display apparatus according to the invention, data of theelectronic card can be displayed on a pixel portion. Further, thereliability of certification of identity can be improved by displaying aphotograph of a face. If a photograph of a face is used instead of apicture for identity, resolution of at least approximately QVGA(320×240) is required.

Example 2

A method for manufacturing a plurality of liquid crystal displayapparatus from a large sized device substrate will be explained withreference to FIGS. 14A and 14B.

A shown in FIGS. 14A and 14B, in case of using a large sized devicesubstrate 601, a plurality of concave portions 603 is formed in areas602, each of which is corresponding to each liquid crystal displayapparatus. LEDs 604 are provided in each concave portion 603. A wiringconnected electrically to the LED 604, an LED driver thin film circuit,a reflection film, or the like (all are not shown) are provided with theLEDs, and a resin 605 is filled with each concave portion 603 as shownin FIG. 14B.

A panel or a thin film circuit is formed and diced in accordance withthe method explained in the embodiment, and a plurality of liquidcrystal display apparatus can be manufactured from one device substrate.The dicing can be carried out either before or after forming the panelor the thin film circuit.

Example 3

In this embodiment, the example that an LED is connected to a flexibleprinted wiring board (FPC) and the FPC is connected to a wiring over adevice substrate, instead that the LED is directly connected to thewiring over a device substrate.

FIG. 15A is a top surface view of an FPC connected with an LED. An LED701 is connected to a lead 702 that is sandwiched by a plastic film 703.A terminal 704 connected with the lead 702 is not covered with theplastic film 703 and is exposed.

FIG. 15B is a view showing the state that the LED 701 illustrated inFIG. 15A is pasted onto a concave portion 705 in the device substrate706. FIG. 15C is a view showing a reverse side of the device substrate706 illustrated in FIG. 15B.

In the device substrate 706, a wiring 707 is provided with a reverseside of the concave portion 705. The LED 701 provided in the concaveportion 705 and the wiring 707 are electrically connected each other bythe lead 702.

The surface of the device substrate 706 provided with the wiring 707 hasa concave portion 710. The regions provided with the concave portions705, 710 are preferably not overlapped each other considering theintensity of the device substrate 706. A solar cell 708 and a drivercircuit 709 for controlling the driving of the solar cell 708 areprovided in the concave portion 710. The wiring 707 is electricallyconnected to the driver circuit 709.

According to the FPC, devices that are provided with both sides of thedevice substrate are electrically connected each other. Thus, the devicesubstrate can be utilized without waste.

FIG. 15D is a cross-sectional view of the concave portion 705 takenalong the dotted line A-A′. A metal reflection film 711 is depositedover the surface of the concave portion 711. According to this example,microscopic irregularities are formed on the surface of the reflectionfilm 711 by corroding and by sandblasting using emery, and light emittedfrom the LED can be diffusely reflected and emitted evenly to the pixelportion.

Example 4

A method for forming a device substrate having a concave portion will beexplained in this example.

FIG. 16A is a view showing a plastic substrate 801 having an openingportion 803 and a plastic substrate 802 that is planarized. The plasticsubstrates 801 and 802 are pasted each other. Then, a device substrate805 having a concave portion 804 is formed in the region where theopening portion 803 overlaps with the plastic substrate 802 that isplanarized.

Example 5

An example that an area sensor is provided with an electronic cardutilizing a liquid crystal display according to the present invention.

FIG. 17A is a view showing that a tip of a finger presses a pixelportion 910 that serves not only as an image display portion but also asan area sensor. FIG. 17B is a view showing a cross-sectional view of thepixel portion 910 illustrated in FIG. 17A.

As shown in FIG. 17B, a device substrate 901 is formed to have a concaveportion 905. A reflection film 902 is formed over the surface of theconcave portion 905. An LED 903 is provided in the concave portion 905and covered with a resin 904.

A TFT 906 for applying voltage to a liquid crystal 907 and a photo diode908 are provided over the device substrate 901. The TFT 906 and thephoto diode 908 are separately formed over different substrates, andseparated to paste onto the device substrate 901.

Light emitted from the LED 903 is reflected by a finger 911 that servesas a subject, and radiated to the photo diode 908. Then, image data ofthe finger 911 can be obtained.

Example 6

A liquid crystal display apparatus according to the present inventioncan be utilized for various electronic appliances. Especially, it iseffective to use the liquid crystal display apparatus for portable typeelectronic appliances since the usability thereof is drasticallyimproved by reducing the weight or the size.

FIG. 18A is a view showing a sheet-shaped cellular phone comprising amain body 2101, a display unit 2103, a sound input unit 2104, a soundoutput unit 2105, a switch 2106, an external connection port 2107, orthe like. An earphone 2108 prepared separately can be connected to thecellular phone via the external connection port 2107. A touch panelliquid crystal display apparatus having a sensor according to thepresent invention is used for the display unit 2103. A continuous streamof operation can be carried out by touching a touch panel operation key2109 displayed on the display unit 2103. A thin film circuit providedwith the liquid crystal display apparatus according to the invention canbe used as various signal processing circuits provided in the main body2101.

FIG. 18B is a view showing an electronic book comprising a main body2201, a display unit 2202, an operation key 2203, and the like. The mainbody 2201 can have a built-in modem. A liquid crystal display apparatushaving a sensor according to the present invention is used for thedisplay unit 2202. A thin film circuit provided with the liquid crystaldisplay apparatus according to the invention can be used as varioussignal processing circuits.

FIG. 18C is a view showing a wrist watch comprising 2301, a display unit2302, a fastening 2303, and the like. A liquid crystal display apparatushaving a sensor according to the present invention is used for thedisplay unit 2302. A thin film circuit provided with the liquid crystaldisplay apparatus according to the invention can be used as varioussignal processing circuits provided in the main body 2301.

FIG. 18D is a view showing a personal computer comprising a main body2401, a display unit 2402, a touch panel key board 2403, a mouse 2404,an external connection port 2405, a power source plug 2406, and thelike. A liquid crystal display apparatus having a sensor according tothe present invention is used for the display unit 2402. A touch panelliquid crystal display apparatus having a sensor according to thepresent invention is used for the touch panel keyboard 2403 and themouse 2404. A continuous stream of operation can be carried out bytouching the touch panel key board 2403 and the mouse 2404. A thin filmcircuit provided with the liquid crystal display apparatus according tothe invention can be used as various signal processing circuits.

FIG. 18E is a view showing a front glass viewing from the inside of acar. A front glass 2501 is pasted with a liquid crystal displayapparatus 2503 according to the present invention. A display unit 2502can display various pieces of information required by a driver. In FIG.18E, an example that the liquid crystal display apparatus according tothe invention is pasted onto the front glass is explained, but theliquid crystal display apparatus can be pasted onto a window glass ofside and back of a driver's seat. Further, the liquid crystal displayapparatus can be pasted onto either inside or outside of a car.

FIG. 18F is a view showing an electronic card comprising a main body2601, a display unit 2602, a connection terminal 2603, and the like. Thepixel portion of the liquid crystal display apparatus according to theinvention can be utilized as the display unit 2602. A thin film circuitprovided with the liquid crystal display apparatus according to theinvention can be used as various signal processing circuits provide inthe main body 2601.

Therefore the applicable range of the invention is extremely large, andthe invention can be utilized for electronic appliances in variousfields. The electronic appliances described in this embodiment can useany structure of liquid crystal structures described in Embodiments 1 to5.

Example 7

A measurement result of a first substrate side after separating and across-section of an insulating film side by TEM will be described inthis example.

On a glass substrate, a W film is deposited to have a thickness of 50 nmby sputtering, a silicon oxide film is deposited to have a thickness of200 nm by sputtering, a silicon oxynitride film is deposited to have athickness of 100 nm by PCVD, an amorphous silicon film is deposited byPCVD to have a thickness of 50 nm as a semiconductor film, sequentially.Thereafter, the resulted film is heat-treated at 500° C. for 1 hour,further, at 550° C. for 4 hours, then, separated by a physical meanssuch as polytetrafluoroethylene tape. FIG. 19 is a TEM photographshowing the W film and an oxide layer at the substrate side. FIG. 20 isa TEM photograph showing an oxide layer and a silicon oxide film at thesemiconductor film side.

As shown in FIG. 19, a metal oxide film is inhomogeneously remained incontact with a metal film. As shown in FIG. 20, a metal oxide film isalso inhomogeneously remained in contact with a metal film. According toboth the TEM photographs, the facts are proved that the metal oxide filmis split off by or separated at boundary faces of both sides, and thatthe metal oxide film is remained inhomogeneously adhered to the metalfilm and the silicon oxide film.

Therefore a quantity of the metal oxide film is attached to the devicesubstrate side of the insulating film in the liquid crystal displayapparatus according to the present invention.

Example 8

A liquid crystal material used for separating a first substrate aftercompleting a liquid crystal display apparatus will be explained in thisexample.

FIGS. 21A and 21B are cross-sectional views showing a liquid crystaldisplay apparatus according to this example. The liquid crystal displayapparatus illustrated in FIG. 21A is provided with a columnar shapedspacer 1401 in a pixel to enhance the adhesiveness of a countersubstrate 1402 and a polarizing plate 1403 at a device side. Accordingto this, a semiconductor device except that in the region that isoverlapped with a sealing member at the separation of the firstsubstrate can be prevented from remaining at the first substrate side.

FIG. 21B a cross-sectional view showing a liquid crystal displayapparatus utilizing a nematic liquid crystal, smectic liquid crystal,ferroelectric liquid crystal or PDLS (polymer dispersed liquid crystal)containing these liquid crystals in polymer resin. The adhesiveness ofthe counter substrate 1402 and the polarizing plate 1403 at a deviceside are enhanced, and a semiconductor device except that in the regionthat is overlapped with a sealing member at the separation of the firstsubstrate can be prevented from remaining at the first substrate side byusing PDLC 1404.

Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention hereinafterdescribed, they should be construed as being included therein.

1. A liquid crystal display apparatus comprising: a liquid crystaldevice having a pixel portion comprising: an insulating film; aplurality of switching elements formed over the insulating film; aplurality of electrodes electrically connected to the plurality ofswitching elements; a liquid crystal material adjacent to the pluralityof electrodes; and a counter substrate opposed to the plurality ofelectrodes with the liquid crystal material interposed therebetween; aback light unit comprising: a plastic substrate; a plurality of lightemitting elements formed over the plastic substrate; and a resincovering the plurality of light emitting elements, and a polarizingplate disposed between the liquid crystal device and the back lightunit, the polarizing plate being attached to the insulating film by anadhesive wherein the insulating film is in direct contact with theadhesive, wherein the polarizing plate is directly attached to the backlight unit, and wherein the plastic substrate covers an entirety of thepixel portion.
 2. A liquid crystal display apparatus comprising: aliquid crystal device having a pixel portion comprising: an insulatingfilm; a plurality of switching elements formed over the insulating film;a plurality of electrodes electrically connected to the plurality ofswitching elements; a liquid crystal material adjacent to the pluralityof electrodes; and a counter substrate opposed to the plurality ofelectrodes with the liquid crystal material interposed therebetween; aback light unit comprising: a plastic substrate; a metal film formedover the plastic substrate; a plurality of light emitting elementsformed over the plastic substrate; and a resin covering the plurality oflight emitting elements, and a polarizing plate disposed between theliquid crystal device and the back light unit, the polarizing platebeing attached to the insulating film by an adhesive wherein theinsulating film is in direct contact with the adhesive, wherein thepolarizing plate is directly attached to the back light unit, andwherein the plastic substrate covers an entirety of the pixel portion.3. A liquid crystal display apparatus according to claim 2, wherein themetal film is sand blasted.
 4. A liquid crystal display apparatusaccording to any one of claims 1 and 2, wherein a liquid crystal cellcomprising a counter electrode, the liquid crystal material, and one ofthe plurality of electrodes is transparent to light.
 5. A liquid crystaldisplay apparatus according to claim 1, wherein the light-emittingdevice is a light-emitting diode.
 6. A liquid crystal display apparatusaccording to claim 5, wherein the light-emitting diode is connected toan FPC and supplied with current via the FPC.
 7. A liquid crystaldisplay apparatus according to claim 2, wherein the light-emittingdevice is a light-emitting diode.
 8. A liquid crystal display apparatusaccording to claim 7, wherein the light-emitting diode is connected toan FPC and supplied with current via the FPC.
 9. A liquid crystaldisplay apparatus according to any one of claims 1 and 2, wherein theliquid crystal display apparatus is incorporated in a cellular phone.10. A liquid crystal display apparatus according to any one of claims 1and 2, wherein the liquid crystal display apparatus is incorporated inan electronic book.
 11. A liquid crystal display apparatus according toany one of claims 1 and 2, wherein the liquid crystal display apparatusis incorporated in a wrist watch.
 12. A liquid crystal display apparatusaccording to any one of claims 1 and 2, wherein the liquid crystaldisplay apparatus is incorporated in a personal computer.
 13. A liquidcrystal display apparatus according to any one of claims 1 and 2,wherein the liquid crystal display apparatus is incorporated in a frontglass.
 14. A liquid crystal display apparatus according to any one ofclaims 1 and 2, wherein the liquid crystal display apparatus isincorporated in an electronic card.
 15. A liquid crystal displayapparatus according to claim 1, wherein the resin comprises atransparent particle.
 16. A liquid crystal display apparatus accordingto claim 2, wherein the resin comprises a transparent particle.
 17. Aliquid crystal display apparatus according to claim 1, wherein thelight-emitting device includes a pair of electrodes.
 18. A liquidcrystal display apparatus according to claim 2, wherein thelight-emitting device includes a pair of electrodes.
 19. A liquidcrystal display apparatus according to any one of claims 1 and 2,wherein the plastic substrate is larger than the counter substrate.